1. Field of the Invention
The present invention is directed generally to a gas laser arrangement including a discharge tube disposed between a cathode and an anode, the discharge tube being provided with a discharge channel and at least one gas return channel.
2. Description of the Related Art
As is known, gas lasers, for example, argon ion lasers generate an output power of up to several watts in the visible range which is suitable for use as a light source for scientific and industrial applications including in spectroscopy, holography and non-destructive materials testing as well as being suitable for use in eye and skin surgery. In a gas laser, a gas discharge is ignited in the discharge channel of the discharge tube between a cathode and an anode. The discharge tube is generally composed of an electrically insulating material which may be, for example, a ceramic such as beryllium oxide (BeO), aluminum nitride (AlN) or aluminum oxide (Al.sub.2 O.sub.3). The discharge tube can also be composed of a cascade, or in succession, of metal discs and insulators. The gas discharge channel in the discharge tube is in the form of a capillary bore having a diameter generally of not more than 3 mm. A gas return channel is provided either as an internal or external connecting channel relative to the discharge tube and extending between the anode space and the cathode space through which gas flows for pressure equalization.
In a known embodiment of a gas laser for generating relatively low power, for example, a ceramic tube is provided for use as a discharge tube the ceramic tube including metallic cooling ribs to eliminate heat. In another embodiment having what is referred to as a stacked structure, the discharge tube is alternately formed of ceramic rings and metallic cooling discs which are each provided with a central bore and are stacked on top of one another in alternation so that the central bores form a discharge channel. In this arrangement, internal gas return paths are formed by a plurality of gas return channels arranged in the discharge tube parallel to the discharge channel. See, for example, U.S. Pat. No. 3,753,144.
A further embodiment of a gas laser for high power use includes a cathode space, a discharge channel, and an anode space are all surrounded by a common discharge tube having a relatively thin wall of ceramic which is cooled by water. The discharge channel is formed of a greater plurality of pot-shaped or cup-shaped, metal elements each of which is provided with a central bore in the base thereof. The metal elements are arranged in succession in the discharge tube. The bores in the cup-shaped elements together form a central discharge channel and are each surrounded by the hollow cylindrical projection or wall of the cup-shaped metal elements. In the region of the bore, a part of the floor or base of the cup-shaped metal elements is composed of a sputter-resistant material such as tungsten. To provide for gas return, the metal elements include additional bores in the region of their edges. In the outer edge region, the metal elements are soldered to the inside wall of the discharge tube. See, for example, U.S. Pat. No. 4,378,600.